learn from your mistakes. (in your games)
Why do I still play poorly

[edit, see post 6 ]
Chess is a very hard game to get good at if you try to learn things about it more than you play actual games against human opponents.
If you understand basic opening ideas (like the center, develop, and castle) and you know the difference between a fork and a pin, then my advice to you would be to put 90-100% of your time into playing human opponents who are ideally + or - 200 points of your strength. I would do this with the goal of losing 100 games before returning to any kind of study with tactics trainer.
If you only play computers and do tactical puzzles, that will make you get better too, but in any case it will just take time. You can keep doing what you're doing but try to get in a game vs a human at least once a week and consider posting a game on the analysis forum to get some ideas from other players.
My 2 cents.
remember that not every position has a tactic. i know as i progress in tactics i often think i have discovered one in a game. i suddenly go from some elaborate mate in 4 to a queen, bishop, and two pawns down.
oh, after reviewing your archive. try longer time controls.

Like seriously; learn to develop your pieces and control the center and your rating will go up a hundred points.
abit more than that.
I'll guarantee a hundred points.
or double his/her money back?

The players have taken the time and interest to provide excellent advice. I am happy that I read their wisdom as I am certain that they will help my game. Always play a standard game with a time control greater then 15 minutes. Observe other games being played. Good luck to you.

Understand the opening is more or less about three things...
There are always exceptions, but these are very fundamental ideas. If you can't preform these things automatically in your games then they're worth reviewing.
Control the center
In the opening stake out some center space by moving one of the center pawns two squares forward. During the middle game try to maintain a pawn in one of the four center squares. If you ever find yourself unable to put a pawn on one of the four center squares, it's often a good plan to work to do so.
Center space is more important than flank space because it will give your pieces the greatest chance of mobility in all three sectors (queenside, middle, and kingside). If you neglect the center, your pieces will have trouble finding useful squares and wont' be able to maneuver where they're needed.
Speed of development
In the opening if you develop only one or two pieces and then try to attack, they won't stand much of a chance against the opponent's whole army. Your pieces are like a team, everyone has to show up and work together to win. In chess "showing up" means moving them off of the back rank and often to a square that influences the center. Pawns do not count as developing moves, pawns stake out space. Try to only make 1 or 2 pawn moves in the opening.
Speed means 1 move each! Don't move the same piece twice in the opening (without good reason) Your development is complete when you're castled and you've cleared your backrank so the rooks can "see" each other. The queen is ideally developed to a square close to her home square. Because of the queen's power, any lesser piece will force her to move again by attacking her, and remember you don't want to move the same piece twice in the opening.
Castling
Of the three this is the only one you may be able to neglect in certain situations... but the great majority of games by masters contain castling and for good reason. It gets your rook out of the corner and puts your king in a safer location. The three pawns extending from the edge of the board will be your king's "pawn shield". Ideally you'll castle to a side that has all 3 pawns, and the "shield" is strongest when none of them have moved yet.
Now read this (or at least look at the few pictures) and you'll have a good idea of what a player generally aims for in the opening.
http://www.chess.com/article/view/3-simple-opening-systems
Like the others said this alone will boost your playing strength by a lot.

This is one reason I like this site so much, great answers for the OP that can only help them improve.
I am spending time doing the daily puzzles, tactics trainer stuff, and playing the computer, I seem to be doing quite well with the puzzles/trainer, but I don't seem to be progressing any in actual playing level. What would be my best course of action?